Traffic monitoring for regulating states of a terminal

ABSTRACT

Embodiments of the invention include a method comprising monitoring a traffic pattern relating to a terminal, and regulating states of the terminal according to the monitored traffic pattern. Other embodiments relate to associated apparatus, communication systems, network elements and computer program products.

FIELD

The present invention relates to the field of telecommunications, and inparticular to methods for conserving battery power in user equipment andreducing unnecessary signaling in telecommunications networks.

BACKGROUND

A communication system can be seen as a facility that enablescommunication sessions between two or more entities such as userequipment and/or other nodes associated with the communication system.The communication may comprise, for example, communication of voice,data, multimedia and so on.

Communication systems providing wireless communication for userequipment are known. Cellular communication systems are configured tohave a cell structure, and typically they support communication withuser equipment changing locations (mobile users). The support forcommunications for mobile users may include support for handing existingconnections from one cell to another cell. At least routing of calls orcommunications for a mobile user in a new cell is typically supported incellular systems. Some examples of a cellular system are the GlobalSystem for Mobile Telecommunications (GSM) and UMTS (Universal MobileTelecommunication System).

A communication system may be circuit switched or packet switched.General Packet Radio Service (GPRS) provides packet-switched dataservices for the GSM and UMTS system.

A technical problem commonly encountered in telecommunications systemsis how to reduce or minimize both power consumption of terminals andunnecessary signaling in the network. The issues of power consumptionand unnecessary signaling are often linked due to the fact that signaltransmission typically accounts for a major part of the overall powerconsumption of a terminal.

Reducing power consumption by terminals is particularly important inmobile telecommunications networks, due to the fact that mobileterminals are typically battery powered and thus have a finite powerreserve. Excessive power consumption by mobile terminals can lead tounacceptably short intervals before the terminal battery needs to berecharged.

Power consumption of mobile terminals can be a particular problem whenthe terminal is running one or more “always-on” applications. Always-onapplications require the terminal to be constantly attached to a radionetwork and to be reachable over the current radio technology. Examplesof always-on applications include push e-mail, instant messaging, andvoice and video telephony.

Many always-on applications need to transmit or receive frequent“keep-alive” messages during the idle times in order to refresh the softstate in the application servers or intermediate firewalls and NetworkAddress Translation (NAT) devices. The keep-alive procedures maymaintain the MS in states which consume so much energy that the batterylifetime will no longer be acceptable. Since IPsec Virtual PrivateNetwork (VPN) and Mobile IP sessions may be used with always-onapplications to provide security and mobility, increasing the powerefficiency of these protocols is particularly important.

Embodiments of the present invention aim to address one or more of theabove-mentioned problems. In particular, embodiments of the presentinvention aim to reduce power consumption and/or unnecessary signallingby terminals in a communications network.

SUMMARY

Accordingly, in one embodiment the present invention provides a method(e.g. for use in a telecommunications system).comprising monitoring atraffic pattern relating to a terminal, and regulating states (e.g.states of the Mobility Management protocol or of the Radio RessourceControl protocol) of the terminal according to the monitored trafficpattern.

In another embodiment, the present invention provides an apparatus (e.g.a network node in a communications system) configured to monitor atraffic pattern relating to a terminal, and regulate states of theterminal according to the monitored traffic pattern.

In another embodiment, the present invention provides a communicationssystem comprising a terminal and a network node, wherein thecommunications systems is configured to monitor a traffic patternrelating to a terminal, and regulate states of the terminal according tothe monitored traffic pattern.

In another embodiment, the present invention provides a network elementcomprising monitoring means for monitoring a traffic pattern relating toa terminal and regulating means for regulating states of the terminalaccording to the monitored traffic pattern.

In another embodiment, the present invention provides a computer programproduct, comprising a set of instructions which when executed by aprocessor in a network node of a communications system, causes thenetwork node to monitor a traffic pattern relating to a terminal, andregulate states of the terminal according to the monitored trafficpattern.

In another embodiment, the present invention provides a computer programcomprising program code means adapted to perform any of the steps of amethod as described above when the program is run on a processor.

In another embodiment, the present invention provides a computer programproduct comprising program code means stored in a computer readablemedium, the program code means being adapted to perform any of the stepsof a method as described above when the program is run on a processor.

Embodiments of the present invention may advantageously reduce powerconsumption and/or unnecessary signalling of terminals by dynamicallyadapting states (e.g. Radio Resource Control or Mobility Managementstates) of a terminal according to the pattern of traffic to/from theterminal. In the absence of such dynamic control, the traffic patternmay greatly affect the amount of time which a terminal spends inparticular radio resource states, which in turn is highly determinativeof the power consumption of the terminal. According to embodiments ofthe present invention, the time spent by the terminal in particularstates can be regulated such that, for example, a power consumptionincrease due to an increase in particular types of traffic is minimized.By monitoring a traffic pattern to/from the terminal, embodiments of thepresent invention allow the configuration of states to be tailored tothe activity and particular requirements of the terminal, and the powerconsumption of the terminal to be kept within acceptable limits. Thiscan increase battery life of the terminal, especially in mobileterminals, as well as freeing radio and SGSN resources.

In some embodiments of the present invention, the states are regulatedthrough timers. After a defined period of time during which the terminalis inactive, e.g. during which the terminal does not transmit or receiveany packet data, the timer expires. Typically the expiry of the timercauses the terminal to transition to a new state with a lower power.Setting of the timer involves defining a length of this period ofinactivity before which the terminal shifts to a less power-consumingstate.

A terminal may have multiple states each having a different powerconsumption, and thus there may be multiple inactivity timers, each ofwhich defines the length of an inactivity period before which theterminal shifts to a less power-consuming state.

In other embodiments, if the frequency of the monitored traffic events(e.g. keep alive messages) increases, a length of the timer period (i.e.the period of inactivity after which the terminal shifts to a lesspower-consuming state) is decreased. This is because if a terminal issending a lot of traffic, such as frequent keep-alive messages, it wouldtend to spend more time in higher power-consuming states and its overallpower consumption would increase. Decreasing the length of one or moretimer periods in this situation minimizes the increase in powerconsumption by ensuring that the terminal returns to a lower power statemore quickly after each transmission event (such as sending or receivinga keep alive message).

Alternatively, if the frequency of keep alive messages decreases, alength of the timer setting is increased. This is because if theterminal is not sending a lot of traffic, its power consumption will belower and it is acceptable for it to spend more time in higher powerstates.

Preferably the traffic monitoring step of the present invention mayinvolve detecting a pattern of transmission of messages to/from theterminal, wherein the messages serve to maintain a connection betweenthe terminal and a further node in the communication system. Morepreferably the monitored traffic comprises keep alive messagestransmitted to/from the terminal. In one embodiment the monitoringcomprises detecting a frequency of transmission of messages such as keepalive messages relating to the terminal.

Preferably the terminal is a mobile terminal, and the network is amobile telecommunications network.

The monitoring step typically results in a set of data, for instance inthe form of a traffic profile, indicative of the traffic patternassociated with the terminal. The method preferably further comprisesstoring this data or profile in a node in the telecommunications system.The data may be stored in any suitable node in the network, for instancein a first controller node having a connection with the terminal. Bycontroller node is meant any node which performs control functionsrelating to a connection between the terminal and another node. Thus insome embodiments, the controller node may be a serving GPRS support node(SGSN) or radio network controller (RNC). The first controller node maybe a node which also performs the monitoring step or may be a differentnode in the communication system.

The method may further comprise transmitting the data to a secondcontroller node, for instance when the terminal establishes a connectionwith the second controller node.

The traffic pattern may be monitored by any suitable node in thecommunications network, for instance a controller node having aconnection with the terminal. Preferably the node performing themonitoring step is an SGSN or RNC serving the terminal.

The regulation of the states of the terminal, for instance the settingof inactivity timers for the terminal, may be performed by any suitablenode in the telecommunications system. In one embodiment, a controllernode (for instance the controller node which performs the trafficmonitoring step) sends an indication of an inactivity timer setting tothe terminal in an attach accept message, a routing area accept messageor a dedicated timer modification message. In the case of attach acceptand routing area accept messages, the timer setting indication is addedto a type of message which carries other data and would anyway betransmitted between the terminal and the node. In the case of adedicated timer modification message, the timer setting indication isprovided in a message specifically transmitted for the purpose ofmodifying the timer.

In other embodiments, the method further comprises monitoring mobilityof the terminal. For instance, the controller node may monitor thefrequency of cell changes of the terminal. Mobility of the terminal maythen be taken into account when regulating the states of the terminal,for instance when setting the inactivity timers, in addition to thetraffic pattern (e.g. the frequency of keep-alive messages) associatedwith the terminal.

If mobility of the terminal decreases, the timer setting (i.e. thelength of the inactive period after which the terminal transitions to alower power state) is preferably increased. This is because if theterminal is relatively static (i.e. its location is not changing), itwill not be sending many cell update messages. Its power consumptionwill therefore be relatively low (compared to a terminal which is highlymobile) and an increasing the amount of time spent in a higher powerstate is acceptable.

In some embodiments, monitoring the traffic pattern of a terminal mayinclude measuring a level of paging traffic associated with theterminal. In lower power states, a terminal may not be able to send orreceive data without transitioning to a higher power state. In order fora terminal in a low power state to receive data, it is often necessaryto page the terminal so that it can shift to a higher power state andreceive the data. The amount of paging traffic may therefore beindicative of the amount of time which the terminal is spending in lowerpower states combined with the frequency with which it issending/receiving keep alive messages. Decreasing the timer settings forterminals sending a lot of keep alive messages according to embodimentsof the present invention may increase the paging traffic, whereasincreasing the timer settings for terminals sending fewer keep alivemessages will tend to reduce paging traffic. Monitoring the level ofpaging traffic to a terminal and taking this into account (along withthe keep alive frequency and optionally also the mobility of theterminal) when setting the timers can help to ensure that the pagingchannel does not become overloaded.

In other embodiments, the monitored traffic data for the terminal (andoptionally further the mobility of the terminal) may additionally beused in setting the value of a periodic routing area update timer forthe terminal.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described by way of example only withreference to the following specific embodiments, in which:

FIG. 1 shows a packet switched mobile telecommunications network in anembodiment of the present invention may be implemented;

FIG. 2 shows radio resource states, inactivity timers and batteryconsumption in a terminal in a 3G mobile network;

FIG. 3 shows features of a serving GPRS support node in an embodiment ofthe present invention;

FIG. 4 shows a flow diagram for practicing an exemplary embodiment ofthe invention.

DETAILED DESCRIPTION OF EMBODIMENTS

FIG. 1 illustrates schematically an example of a cellular networksupporting packet-switched services in which the present invention maybe implemented. The network 100 may be a 2G GPRS or a 3G GPRS network.Alternatively, the system 100 may be an EDGE/EGPRS network. Only some ofthe network elements of a 2G/3G network are illustrated in FIG. 1.

The radio access network comprises a number of base station systems.Each base station system comprises a base station controller (BSC) 4 anda number of base stations (BS) 5, 6. A terminal or mobile station (MS) 7communicates with a base station 5 over a radio interface. Thepacket-switched core network of the system 100 comprises a number ofGPRS Supporting Nodes (GSN). Each mobile station registered forpacket-switched services has a serving GSN, called SGSN, 3 which isresponsible for controlling the packet-switched connections to and fromthe mobile station. The packet-switched core network is typicallyconnected to further packet-switched networks via a Gateway GSN (GGSN)2. Services may be provided to the mobile station from an applicationserver 1 connected to the GGSN 2.

In a cellular network, the MS 7 can be in a number of different statesdepending if it is transmitting data, or has transmitted data recentlyor not. The state has a significant impact on the power consumption ofmobile terminals in the network.

In 2G GPRS a terminal can be either in the state Ready (in which the MSis tracked at cell level) or the state Stand-by (MS tracked in RoutingArea (RA) level, A routing area comprising many cells). In the readystate, cell updates are required each time the MS changes cell. In thestand-by state, The MS only needs to send updates when changing RA andthe MS will be paged in the RA in case of a downlink packet.

FIG. 2 illustrates the states in a 3G GPRS network. The terminal is inone of the following states:

-   -   CELL_DCH (Dedicated Channel). The MS is tracked at cell level.        In this state, the current consumption is at its highest,        comparable to the consumption during circuit-switched voice        calls. The current consumption is around 220 mA or higher. The        phone has a dedicated channel, which it does not share with        other phones, so maximum throughput and minimum delay are        achieved.    -   CELL_FACH (Forward Access Channel). MS tracked at cell level. In        this state, the phone shares the channel with other phones. This        state is used when there is not much traffic to transmit. The        battery consumption is roughly half of the consumption in the        CELL_DCH state. The current consumption is roughly 120 mA.    -   CELL_PCH (Paging Channel). MS tracked at cell level. This        optional state offers the lowest current consumption of around        1-2 percent of the consumption in CELL_DCH state (around 4 mA).        If there are downlink packets for the terminal, the terminal        will be paged. In this state, the terminal is not able to send        or receive packets, but the terminal will have to enter either        the CELL_DCH or CELL_FACH state to send or receive. Not all        network implementations currently use the CELL_PCH state.    -   URA_PCH. MS tracked at UTRAN Registration Area (URA) level. If        there are downlink packets for the terminal, the terminal will        be paged in the URA. There are less updates but more paging than        CELL_PCH. This state provides the same benefits as CELL_PCH and        further enhances the battery performance when there is mobility.    -   Idle mode. MS tracked at Routing Area level by the SGSN and        there are no context in RNC. In this state, the phone does not        have an RRC connection, so it is not possible to send or receive        packets in this state. The terminal can still have a PDP context        and it can be reached by paging procedures, after which the        terminal can leave the idle mode and receive downlink packets.        However an RRC connection will have to be established before the        downlink packets can be received.

State transitions are based either on explicit signaling or inactivitytimers. The timers T1, T2 and T3 are shown in FIG. 1. The names T1, T2and T3 are not officially used in 3GPP specifications but they haveestablished in WCDMA parlance. The timers are network controlled andmanaged by the Radio Network Controller (RNC). The timers are discussedbelow:

-   -   T1 is an inactivity timer that is used in the CELL_DCH state.        This timer is reset whenever there is traffic. The timer will        expire only after an inactive period of T1, and the terminal        will enter the CELL_FACH state. The shorter the T1 timer, the        worse the user experience will be e.g. in web browsing. The T1        value may depend on the DCH data rate. The default values used        in the Nokia RNC implementation are 5 seconds for 8-32 kbit/s, 3        seconds for 128 kbit/s, and 2 seconds for data rates greater        than 128 kbit/s. In some networks, significantly longer timers        than the Nokia defaults may be used.    -   T2 is an inactivity timer in the CELL_FACH state. If CELL_PCH is        used, the state machine will enter the CELL_PCH state after an        inactivity period of T2. If CELL_PCH is not used, then the state        machine will enter the idle state. The default value in Nokia's        implementation is 2 seconds, but often significantly longer T2        values are used.    -   T3 is a timer used in CELL_PCH (and in the URA_PCH state that        may be introduced in the future). After staying in the CELL_PCH        or URA_PCH for T3 seconds, the RRC connection will be released.        This is typically a very long timer (several minutes or even        tens of minutes).

The inactivity timers T1 and T2 define the time after which the phonetransitions from the more power-consuming states to less consumingstates. The sum T1+T2 defines the general power consumption behavior ofthe device, and the value of T1 has a significant effect on theperceived performance of several applications.

Always-on applications require the terminal to be constantly attached toa radio network. In order to keep the connection active, many always-onapplications require that frequent keep-alive messages are transmittedbetween the terminal and a server node in the network, for examplebetween the mobile station 7 and the application server 1 shown in FIG.1

Transmission of a keep alive message (like any packet) moves the mobilestation into, or maintains the MS in a high power state (e.g. Readystate in 2G, CELL_DCH or CELL_FACH in 3G).

It is often assumed that in packet based cellular networks, after apacket transmission the probability of a new packet transmission withina short period of time (e.g. up to a few seconds) is quite high. Butthis assumption is not true with respect to keep alive messages.

Many applications tend to send keep alive message regularly, but atintervals of 15 seconds to 10 minutes. For example, Skype sends clientoriginated keep-alive every 60 seconds. Nokia Email has a keep-alivesent by server every 4 minutes. A VPN client behind a NAT might sendkeep-alive every 30 seconds.

With keep alive intervals within this range, the MS may be most of thetime in an high power state (in 2G GPRS_Ready; in 3G PMM ConnectedDCH/FACH), as short data transmissions are sent/received only atregularly spaced intervals. This uses a lot of unnecessary batterypower. In addition, it requires a lot of radio signalling (compared tothe amount of data transferred) and thus consumes network resources.Transferring keep alive is not very cost efficient for operators.

One way in which this problem could be addressed is by using timers inthe radio optimised for keep-alive. For example, the length of timerssuch as T2 can be kept short, e.g. around 2 s. However these timers maynot be optimised for other applications like browsing. Today operatorshave asked for T2=120 seconds probably due to browsing behaviour.

According to one embodiment of the present invention, radio and mobilitymanagement timers are adapted dynamically depending on the pattern oftraffic used. A node such as an SGSN or RNC controls timer setting by:

-   -   monitoring the traffic pattern of one subscriber;    -   detecting a keep alive pattern;    -   storing traffic characteristics in a context related to the        terminal; and    -   adapting timers to fit best the mobile traffic type.

The traffic characteristics (e.g. TCP keep-alive every 60 s, MSinitiated) are stored in a new field “traffic profile” in the subscribercontext (in SGSN or RNC), and transferred to a new node due to mobilityevents (such as inter SGSN RA update; SRNC relocation).

The following specific embodiment is discussed with respect to a 2G GPRSnetwork. In other embodiments, the method can be applied to a 3G networkin a similar way.

FIG. 4 shows a flow diagram of how one embodiment of the presentinvention may be implemented in a GPRS network 100 as shown in FIG. 1.At step 41, an SGSN 3 sends attach accept and RA update accept messagesto a mobile terminal 7. These messages may include a ready timer and/ora periodic RA update timer, by which it is meant that the SGSN 3indicates to the mobile terminal 7 in one or more such messages asetting for a length or period for these timers. The setting of theready timer, for example, defines the length of a period of time, afterwhich the terminal shifts from the ready to the standby state, if theterminal is inactive during that period.

For MS who initiate keep-alive regularly, the ready timer should be keptvery short in order to reduce the amount of cell updates after atransmission. A value of 5 to 10 second should be appropriate. Thedrawback of this is that the amount of paging would increase. Theoperator could consider reducing the size of the RA to reduce pagingload. A relative short value of the periodic Routing area update (e.g.30 minutes) should also be appropriate (Normally these MS will notperform periodic RA update due to frequent packet transmission. However,if they move out of coverage, the periodic RA update will expire andpaging will be suspended. It will save paging capacity). However, such asetting would not be optimal for other users who are not having regularkeep-alive message.

Thus according to one embodiment of the present invention, the SGSN 3initially (e.g. at attach) sends to the MS 7 a short Ready timer setting(5-10 seconds) and a short periodic RA Update timer (20-40 minutes).These timers are set to a value adapted for users having regularkeep-alive.

At step 42, the SGSN 3 starts to monitor the traffic pattern, and atstep 43 stores in the subscriber specific traffic profile informationrelated to the usage of keep-alive. In particular, the mobile station 7may be sending keep alive messages to the application server 1 in orderto maintain a connection necessary for the server 1 to provide a serviceto the MS 7. If the user is not sending keep-alive messages at or abovea predefined frequency, in the next RAU response the SGSN 3 resets thetimers to a different setting more appropriate for a terminal which isnot sending regular keep-alive messages. For example, the Ready timer isset to 60 seconds and the periodic RA Update timer is set to 2 hours(see step 44 in FIG. 4).

The SGSN 3 keeps monitoring the traffic pattern of this subscriber, asthe user might activate a new application on his phone. At the next RAupdate the SGSN 3 again sets the timers appropriately based on thelatest traffic pattern of the user. For instance, if activation of a newapplication leads to an increase in the frequency of keep alivemessages, the SGSN may decrease the length of the timer setting (seestep 45).

It should be noted that if the MS 7 is not moving (so no RA update istriggered by movement) and sending traffic regularly, (periodic RAupdate timer never expires), the SGSN 3 may not be able to modify thetimers. Using a small RA size will increase the probability that theuser cross a RA border.

In certain cases, the SGSN 3 may want to modify the timers, but may notreceive RA updates. In that case, the SGSN 3 sends a message to the MS 7to trigger a modification of the timers. This message may be sentaccording to a “timer modification procedure”, a dedicated message whichcan be used to reset the timers and generate a RA update.

One way in which to reset the timers would be for the SGSN 3 to detachan MS with a reattach indication. The SGSN 3 may take into account theload on a paging channel when setting the timers. The SGSN 3 may forexample detect that a paging channel is overloaded and/or that certainMS 7 generate a lot of paging. Typically that could be the case ifkeep-alive is generated from the server, and the keep-alive intervalsare short. In this case the SGSN 3 detaches the MS 7, forcing it tore-attach and then sets a longer ready timer (reducing paging load atthe expense of cell update load). Although in this embodiment the powerconsumption of the terminal may increase, in certain circumstances itmay be necessary to avoid overloading on the paging channel.

The method may be controlled by a traffic detection engine in, forexample, an SGSN 3 or BSC/RNC 4. FIG. 3 shows in more detail the SGSN 3in which are represented certain features of one embodiment of thepresent invention. The SGSN 3 comprises a timer regulating/setting means31, which may comprise a transmission means for sending timer settingmessages to the BSC/RNC 4 for forwarding to the MS 7. The SGSN 3 alsocomprises a traffic monitoring means/traffic detection engine 32 whichcollects the relevant data relating to the MS 7. The data may be storedin a traffic profile field along with other data relating to thesubscriber of the MS 7, in a storage means 34 also provided in the SGSN3. Processes performed by the SGSN 3 may be controlled by a suitablyprogrammed processor means 33.

In one embodiment the traffic detection engine 32 is able to derive thenumber and/or frequency of keep-alive messages transmitted to/from theterminal 7. Different applications running on a single MS may generateor require their own keep alive messages. Thus each keep-aliveapplication should have a profile containing the following information:

-   -   keep-alive frequency;    -   keep alive direction;    -   keep-alive L3/L4 characteristics (IP address/port numbers);    -   paging frequency.

In a further embodiment, the SGSN 3 also monitors the mobility of theuser. For example, the SGSN 3 may monitor the frequency of cell changes.If the user has not changed cell for an extended period, e.g. at least24 hours, the SGSN 3 may determine that the MS 7 is static and increasethe ready timer value (the MS is not sending cell updates so it can stayin the ready state for longer).

In one embodiment employing a 2G GPRS network, the timers are initiallyset based on traffic profile, but these settings can be modified oroverruled based on mobility data of the terminal, e.g. if the MS 7 isstatic.

In another embodiment, the traffic profile is sent between nodes duringinter SGSN Routing Area Update, Intersystem inter SGSN RA update, orSRNC relocation. This may be done because it takes time to determine atraffic pattern (to be accurate it might be worth waiting for 3consecutive keep alive messages which can take 10-20 minutes). Bysending the traffic profile to a new node with which the terminal hasjust established a connection, the new node can immediately set itstimer accordingly.

Although the above embodiments have been described with respect to a 2GGPRS network, the method may also be implemented with timers in 3Gnetworks. In 3G networks such as UMTS and WCDMA, key timers regulatingRadio Resource Control states are controlled by the RNC. Thus inalternative embodiments employing 3G networks, an RNC operates the samepattern detection mechanism and modifies the timers accordingly. Infurther embodiments implemented in 3G networks, the pattern detection isperformed in a 3G SGSN, and the results or timers setting are sent tothe RNC during RAB establishment or RAB modification. If the patternchanges (for instance if the user activates a new application), the SGSNdetects this and sends a RAB modification to the RNC. The RNC thenadjusts its timers.

Embodiments of the present invention are applicable to all wirelesspacket technology, and so may also be applied to WiMAX or 3.9G (alsoreferred to as 3G long-term evolution or 3G LTE) networks.

Although in the appended claims the dependant claims refer only to anindependent claim on which they depend, embodiments of the presentinvention may encompass any combination of features disclosed in theclaims. In particular, embodiments of the present invention may comprisefeatures from any two or more dependant claims in combination with anindependent claim on which they depend.

1. A method comprising: a) monitoring, by a node of a packet switchedcore network, a traffic pattern relating to a terminal; and b)regulating states of the terminal according to the monitored trafficpattern, wherein the monitored traffic pattern comprises a keep alivemessage pattern relating to keep alive messages transmitted by theterminal; and further comprising, between monitoring and regulating,detecting a keep alive pattern and deriving from the detected keep alivepattern a keep-alive profile including information about at least two ofa keep alive frequency, a keep alive direction, and keep alive L3/L4characteristics regarding an internet protocol address/port number.
 2. Amethod according to claim 1, wherein the step of regulating statescomprises setting a timer of the terminal.
 3. A method according toclaim 2, wherein the setting of the timer defines a period after whichthe terminal shifts to a state having a lower power consumption, if theterminal is inactive during the period.
 4. A method according to claim3, wherein if a frequency of the keep alive messages decreases, a lengthof the period is increased.
 5. A method according to claim 3, wherein ifa frequency of the keep alive messages increases, a length of the periodis decreased.
 6. A method according to claim 1, wherein the terminal isa mobile terminal.
 7. A method according to claim 1, further comprisingstoring data indicative of the monitored traffic pattern in the node. 8.A method according to claim 7, wherein the node is a first controllernode having a connection with the terminal.
 9. A method according toclaim 8, further comprising transmitting the data to a second controllernode when the terminal establishes a connection with the secondcontroller node.
 10. A method according to claim 1, wherein the node ishaving a connection with the terminal.
 11. A method according to claim10, wherein the controller node sends an indication of a timer settingto the terminal in an attached accept message, a routing area acceptmessage or a dedicated timer modification message.
 12. A methodaccording to claim 1, further comprising monitoring, by the node of thepacket switched core network, mobility of the terminal.
 13. A methodaccording to claim 12, comprising setting a timer according to themonitored mobility of the terminal and the monitored traffic pattern ofthe terminal.
 14. A method according to claim 12, wherein if mobility ofthe terminal decreases, a length of a period of inactivity after whichthe timer expires is increased.
 15. A method according to claim 1,wherein the monitored traffic pattern comprises a level of pagingtraffic associated with the terminal.
 16. A method according to claim 1,further comprising setting a periodic routing area update timer for theterminal according to at least one of the monitored traffic pattern andmobility of the terminal.
 17. A method according to claim 1, wherein thenode of the packet switched core network comprises a serving generalpurpose radio service support node.
 18. An apparatus configured to: a)monitor a traffic pattern relating to a terminal; and b) regulate statesof the terminal according to the monitored traffic pattern, wherein theapparatus comprises a node of a packet switched core network, whereinthe monitored traffic pattern comprises a keep alive message patternrelating to keep alive messages transmitted by the terminal; and furtherconfigured, between monitoring and regulating, to detect a keep alivepattern and deriving from the detected keep alive pattern a keep-aliveprofile including information about at least two of a keep alivefrequency, a keep alive direction, and keep alive L3/L4 characteristicsregarding an internet protocol address/port number.
 19. An apparatusaccording to claim 18, which is configured to regulate states by settinga timer of the terminal.
 20. An apparatus according to claim 18, whereinthe node of the packet switched core network comprises a serving generalpurpose radio service support node.
 21. A non-transitory computerreadable storage medium embodied with a computer program comprising aset of instructions which when executed by a processor in a node of apacket switched core network of a communications system, causes the nodeof the packet switched core network to a) monitor a traffic patternrelating to a terminal, and b) regulate states of the terminal accordingto the monitored traffic pattern, wherein the monitored traffic patterncomprises a keep alive message pattern relating to keep alive messagestransmitted by the terminal; and further between monitoring andregulating, to detect a keep alive pattern and deriving from thedetected keep alive pattern a keep-alive profile including informationabout at least two of a keep alive frequency, a keep alive direction,and keep alive L3/L4 characteristics regarding an internet protocoladdress/port number.
 22. A non-transitory computer readable storagemedium according to claim 21, wherein the node of the packet switchedcore network comprises a serving general purpose radio service supportnode.
 23. A method comprising: a) monitoring. by a node of a packetswitched core network, a traffic pattern relating to a terminal; and b)regulating states of the terminal according to the monitored trafficpattern, wherein the monitored traffic pattern comprises a keep alivemessage pattern relating to keep alive messages transmitted by theterminal; and further comprising, between monitoring and regulating.detecting a keep alive pattern and deriving from the detected keep alivepattern a keep-alive profile including information about at least two ofa paging frequency, a keep alive direction, and keep alive L3/L4characteristics regarding an internet protocol address/port number.